1. Field of the Invention
The present invention relates to a liquid ejection head, and more particularly, to technology for achieving high density arrangement of wiring, drive circuits, and the like, of drive elements which apply an ejection force to liquid to be ejected from ejection holes.
2. Description of the Related Art
In recent years, inkjet recording apparatuses have come to be used widely as data output apparatuses for outputting images, documents, or the like. An inkjet recording apparatus forms an image, document, or the like, corresponding to data, on a medium by ejecting ink from nozzles, by driving actuators corresponding to nozzles provided in a print head, in accordance with data.
There have been increasingly demands for improved quality in the image produced by inkjet recording apparatuses. By creating an image by means of dots of very small size arranged at high resolution, improved quality in the final image can be achieved. In order to achieve a very small dot size, it is necessary to make the nozzle diameter very small, thereby achieving a very small volume in the ink droplets ejected from the nozzles in each ejection operation. Furthermore, in order to achieve a high-resolution arrangement of dots, the nozzle density should be increased and droplet ejection control suited to the increased resolution of the dot arrangement should be implemented.
Furthermore, in a composition where an ink ejection force is obtained by means of actuators, such as piezoelectric elements, then if the density of the nozzle arrangement is increased, the actuators are also disposed at high density in accordance with nozzle arrangement. When actuators are disposed at high density, it is difficult to arrange the wires which transmit drive signals to the actuators on the surface on which the actuators are installed, and a high-density arrangement of the actuators and the wires to the actuators is achieved by firstly extending the wires in a perpendicular direction from the surface where the actuators are installed, and then arranging the wires in a horizontal direction, by using a wiring member such as a flexible printed circuit formed with multiple layers.
Japanese Patent Application Publication No. 2003-136721 discloses an actuator apparatus, an inkjet type recording head and an inkjet type recording apparatus, in which a junction member is bonded to a flow channel forming substrate in which nozzles, pressure chambers, and the like, are formed. The junction member is placed on the side of the flow channel forming substrate on which the piezoelectric elements are arranged. An installation section to which external wires are connected is arranged in a region on the junction member reverse to the side of the piezoelectric elements, and drive wires are arranged on the junction member, one end of each wire being connected to the installation section and the other end of each wire being connected to each piezoelectric element. The structure of the inkjet recording head is thereby simplified and reduced in size.
Japanese Patent Application Publication No. 2003-251813 discloses an inkjet head, an inkjet recording apparatus and a laminated piezoelectric element, in which external electrodes extend onto a step section of piezoelectric elements having an L-shaped cross-section and are arranged into through holes in a laminated ceramic substrate by wire bonding. A driver IC (integrated circuit) to which the external electrodes are electrically connected is installed on the surface of the laminated ceramic substrate reverse to the surface thereof where the piezoelectric elements are arranged. Therefore, the operability and reliability of the wiring to the piezoelectric elements is improved, and an inkjet head having a simple and compact structure is obtained.
Japanese Patent Application Publication No. 9-327912 discloses a recording head, in which an inkjet recording head is composed by a junction-free, single-plate silicon monocrystalline substrate, in which nozzles, pressure chambers, a diaphragm, a common ink chamber, and the like, are formed, and a head frame section, and therefore the head has few constituent parts and the head structure is simple.
However, if a wiring member, such as a flexible printed circuit, is used to extend wires from the actuators in a horizontal direction, then the current capacity and size of the wiring member place limitations on the extent to which wiring density can be increased. For example, if a flexible printed circuit is used as a wiring member, then although it is possible to increase the wiring density by building the flexible printed circuit with multiple layers, considerations such as the difficulty of manufacture and the strength place limits on the multi-layer structure that can be achieved in the flexible printed circuit.
Furthermore, in order to reduce the size of the head, it is possible to install a drive circuit for driving the actuators, on a flexible printed circuit as described above, or on a structural member of the head, but the heat generated by this drive circuit may cause increased temperature variation in the ink. If there is increased temperature variation in the ink, then this can lead to unstable ejection, and a significant decline in ejection performance.
In the actuator apparatus, inkjet recording head and inkjet recording apparatus disclosed in Japanese Patent Application Publication No. 2003-136721, it is necessary to position the members with high precision when bonding the junction member with the flow channel forming substrate, and therefore, the manufacturing process is difficult. Furthermore, due to the heat radiation design of the installation section connected to the junction member, the heat generated by the drive circuit (driver IC) mounted on the installation section is transmitted to the flow channel forming substrate, and there is a probability that this may cause a change in the temperature of the ink inside the pressure generating chambers.
Moreover, in the inkjet head, inkjet recording apparatus and laminated piezoelectric elements disclosed in Japanese Patent Application Publication No. 2003-251813, since the piezoelectric elements are formed with the L-shaped cross-section, the manufacture of the piezoelectric elements is complicated, and the difficulty of manufacturing the piezoelectric elements is increased. Furthermore, the presence of the step sections onto which the external electrodes of the piezoelectric elements extend obstructs a high-density arrangement of the piezoelectric elements.
Furthermore, Japanese Patent Application Publication No. 9-237912 only discloses technology for achieving a simple structure having a small number of constituent parts, but it does not discuss how to achieve. a high density arrangement in the recording head.